Tunneling hot-electron transistors are quantum-effect devices because certain structures within the transistors are typically less than 100 .ANG.. Tunneling hot-electron transistors operate by injecting high energy electrons from the emitter into the base of the transistor by a tunnel injector interposed between the emitter and base. By applying a potential to the emitter-base junction, the tunnel injector provides sufficient energy to the electrons in the emitter so that the electrons are transported across the base to the collector of the transistor. The injected high energy electrons from the emitter are referred to as hot-electrons. The injection of hot-electrons into the base provides the gain of a hot-electron transistor. Tunneling hot-electron transistors are desirable for their small size, high gain, high speed, and low operating voltages.
Currently available tunneling hot-electron transistors do not operate effectively at room temperature (300.degree. K.). Previously developed tunneling hot-electron transistors require cooling (typically 77.degree. K.) before they are functional. This requirement of cooling is a major limitation on the practicality of conventional tunneling hot-electron devices. Cooling the transistors generally involves the use of expensive and complicated equipment. The need for cooling prevents previously developed tunneling hot-electron transistors from achieving commercial viability and widespread use.
Another disadvantage of previously developed hot-electron transistors is that they experience high leakage currents at temperatures approaching room temperature that prevent achieving the desired gain. Presently developed tunneling hot-electron transistors, therefore, do not provide the desired performance at room temperature.
Hot-electron transistors utilizing a double-tunnel barrier or resonant-tunnel barrier for injecting the hot-electrons from the emitter into the base have also been developed. Resonant-tunneling hot-election transistors have been shown to operate at room temperature. However, gain characteristics of resonant-tunneling hot-election transistors at room temperature are a strong function of bias voltage which precludes their use in many applications.
Transistors utilizing high energy band gap materials to create hot-electrons have been previously developed. These transistors do not rely on tunnel barrier transport generation of the hot-electrons, but present a difficult material system that is hard to reproduce resulting in poor yields.